KOC has been producing oil using dual completions from different pressure regime zones from the same well and South East Kuwait field has many such dual completions wells which are currently being converted from natural flow completion to artificial lift completions. In one of such dual completion naturally producing well, first time in world an artificial lift system - Anchor Pump was installed in Short String (SS) through rigless intervention. Thus project well had un conventional dual completion in the field first of its kind i.e. Sucker Rod Pump (SRP) installed in short string and natural producer through Long String(LS). The well produced for some time through both strings and an intervention by workover rig was required due to high water cut and stuck anchor pump in short string. The paper describes the challenges and initiatives and learnings for safe execution of unconventional dual completion well workover.

Due to combination of natural flow and SRP artificial lift completion, the X-mas tree configuration and associated surface equipment of such well was had several constraints and HSE issues for mobilization of rig and dual production zones with varying pressure regimes have challenges of initial well killing due to plugged short string by stuck anchor pump. The risks were identified during planning stage and risk reduction measures were jointly agreed with Field Development. Various options were explored to minimize risks to ALARP level and subsequently addressed in Work Over Program. The surface equipment constraints were eliminated through rigless works and X-tree configuration were modified to suit deployment of a workover rig. Well process safety principles were applied to accomplish initial well killing in both production zones so as to safely pull out existing dual string completion without any well control issues. An initiative to use sucker rod back off tool, first time and safe back off operation was performed successfully from very close to stuck point.

The existing completion strings were pulled out and further well cleanout and workover program was well cleanout Finally, well was completed with new ESP completion string and successfully production tested. The most important factor in success was proactive planning keeping in view of Process Safety for well control issues and effective communication among the concerned parties.

The initiatives adopted in execution of such a challenging well intervention resulted enhancement in safety to rig crew and Rig operational safety standards in addition to contribution towards cost reduction. Lessons learnt has potential of rig time saving specially during workover of large number of heavy oil wells where stuck sucker rod conditions are very common due to sand invasion in tubing during production.

The case study describes a modeling and simulation study of an inverted ESP completion to address three fundamental objectives. A) Increasing the ultimate oil recovery in the massive sands of Cretaceous age in Greater Burgan field by managing water production B) Mitigating the rapid water coning conditions in this high permeable water drive reservoir and C) Designing an optimal operating strategy with Downhole Water Sink (DWS) to control water production and manage well performance. A 2×2km sector was carved out from the full field geological model with 12 wells including the study well. The study well was producing at high water cut at the time of the study. All static properties were updated, and the model was history matched for production, pressure and saturation. Several sensitivity runs were performed, and prediction scenarios were run for 5 years to observe well production behavior in time. The well model was setup with an inverted ESP between straddle packers to produce water from below OWC and inject into bottom reservoir with a production string above to produce from the oil zone. This setting ensured a reverse oil cone being generated from below OWC in the reservoir under production. The aquifer model was finite in size enabling bottom water influx. Simulation results showed that implementation of DWS technology made the water production reduced by 18% during five years with an increase in oil production of nearly 25% in the study well. To maintain continuous well offtake rate, a range of water rates to be produced and injected to bottom reservoir have been studied. Several iterative runs were made to investigate the best completion interval and injection & production rates. The profiles of oil water interface near well bore indicated good reduction in the cone height as compared to normal completion. The results also showed significant improvement in oil recovery within the drainage radius of the well from the simulations. Simulation results provided good understanding of the saturation change near well bore area under different production rates. Prediction runs were made for sustainable oil production under natural flowing condition and the conditions to switch over to production under artificial lift. Production of thin layers of remaining oil from within high permeable massive Burgan middle sands has been a high concern due to very high water cuts because of coning. The study results have provided encouraging option with DWS technique to improve recovery from the reservoir.

In the current and future scenario of increasing demand for hydrocarbons, Multi-Disciplinary Integrated Reservoir Management team is the key to achieve maximum production rates and ultimate recovery. In Raudhatain Upper Burgan reservoir production started in 1959 with initial reservoir pressure of 3850 psi. Decline in reservoir pressure with sustained rate of production indicated weak aquifer support and initiated water injection during the year 2001 with three flank injectors. Production rate was sustained at 30 to 35 MBOPD for long time and it was decided that to go the next level of production and to meet KOC's strategic production target.

Various alternative pressures – production plans were scrutinized by the multi-disciplinary team consists of Geologists, Reservoir Engineers, Petrophysicists and Petroleum Engineers and identified bottlenecks, constraints and action plan to address the problems and to accelerate the production. Some of the bottlenecks to accelerate the production were decreasing pressure, unavailability of required volume of water for injection, delay in commissioning of effluent water injection facility and low productivity of flank wells with viscous oil. The integrated Reservoir management team initiated number of projects to increase the productivity like Paradigm shift in drilling practice by way of drilling Horizontal, Multilateral wells and completing with ICD's for better production and injection sweep efficiency. Liquidated the sick wells with no potential in any other Reservoirs (Multiple Reservoirs) are identified for Horizontal Sidetracking to sweet spot areas. Decreasing Reservoir pressure and Voidage Replacement Ratio has been addressed by changing the water injection strategy and aligning the injectors in right areas.

The results were rewarding as the production rate doubled from a sustained level of 35 MBOPD to more than 70 MBOPD in a span of 3 to 4 years. The initiatives taken to convert the producers to injectors resulted in increased water injection volume and doubled the Voidage Replacement Ratio.

This paper presents the details of Integrated Reservoir Management team efforts and what are the initiatives and strategic actions taken by overcoming the current constraints to double its production. It discusses the effective Reservoir Management of a mature oil field to enhance and accelerate production.

To optimize production from a key reservoir, obtaining a core sample with minimum fluid invasion and damage was necessary. In addition, operational nonproductive time (NPT) related to drilling challenges, such as interbedded formations of varying formation pressures, wellbore instability in the reactive, stressed shale sections, and hole cleaning concerns, needed to be mitigated. This paper describes the design of the drilling fluid and its performance in the field.

After completion of the first dump flood water injection well drilled using an 80/20 conventional nonaqueous fluid (NAF) weighted with barite, low injectivity was observed, which led to acquiring cores to analyze permeability and porosity along with the change in mineralogy resulting from long exposure of the reservoir in the water zone. A 70/30 organophilic clay-free (OCF) NAF was selected to mitigate equivalent circulating density (ECD) risks and minimize damage. Proprietary software was used to customize the bridging design, which was verified during laboratory testing, and to help ensure adequate hole cleaning with the customized low-ECD fluid.

The engineered OCF NAF contained no damaging materials, such as barite, asphaltic material, or organophilic clay. OCF NAFs are well suited to low-ECD drilling operations because they are more resistant to weighting material sag than conventional NAF systems of similar rheology. This is a product of the high gel strengths developed, even in low-rheology (low-ECD) fluids. Downhole pressure fluctuations are low because these gels are fragile and break easily. For the well in which this OCF NAF was used, drilling, coring, and logging operations were successfully completed without incident. Four cores were acquired with minimal damage compared to the previous wells resulting from the engineered design of the bridging material and fluid-loss control polymers. In addition, there was minimal erosion to these four cores, which was a result of the low-ECD fragile gel fluid used. The fluid-loss control properties of the fluid were also effective in strengthening the wellbore and eliminating differential stuck pipe tendencies that had been observed in previous wells. The fluid properties resulted in minimal ECD, and the OCF NAF displayed excellent suspension along with improved pressure management; no pressure spikes occurred while breaking circulation. There was no NPT related to wellbore instability or any of the drilling challenges previously identified.

This unique organophilic clay-free and organolignite-free drilling and coring fluid relies on a specialized technology involving an interaction between the emulsifier package and the polymer additives in the fluid. This provides the behaviors needed for reliable weight material suspension and suitable hole cleaning properties in a low-ECD drilling fluid. Together with the appropriately designed bridging package, the OCF NAF provided a better understanding of the reservoir characteristics by delivering the core with minimal damage.

Sabriyah Lower Burgan (SALB) is a multi-billion-barrel reservoir located in north Kuwait with favorable fluid and rock properties, and a strong active aquifer. The presence of the aquifer is advantageous for primary development of the reservoir but presents a challenge for conventional application of chemical EOR (CEOR). SALB has passed multiple stages of a CEOR evaluation process (technical screening, laboratory formulation design, SWCT, pilot design, risk assessment, etc.), and is currently considered for a multi-well CEOR pilot. This study investigates the viability of using sacrificial wells in the management of the lateral aquifer present in the SALB Layered formation, which represents a sought after CEOR target. The objective of these sacrificial wells is to reduce the potential negative impacts of the existing aquifer on commercial CEOR deployment.

The adopted approach involved using a history matched field model with EOR parameters calibrated to laboratory results for ASP and CO2 technologies. The multi-well field model was used to evaluate and compare different development scenarios to assess the impact of sacrificial wells. These scenarios were evaluated based on production performance and economics.

It was observed that strong aquifer presence complicates both CO2 and ASP project implementation. Challenges due to the aquifer include loss of EOR agents into the water leg, difficulty in accounting for effective pore volume of the project and water encroachment. It is difficult for EOR project economics to compete with an effective aquifer primary development. Sacrificial wells can be used to reduce the strength of the aquifer, potentially improving the effectiveness of the EOR technology. Although the sacrificial wells are unlikely to be economic on their own, they can improve the overall economics of the project. The amount of recovered oil due to EOR deployment is an important parameter to evaluate the economic feasibility of using sacrificial wells.

Many reservoirs around the world have strong aquifers, for which conventional reservoir engineering advice has been to avoid EOR application. This paper introduces a novel approach to deal with these strong aquifers by strategically placing wells that can reduce the aquifer's strength, thus making EOR deployment more favorable.

The 12-1/4-in. directional application is one of the most challenging applications in North Kuwait. The section requires drilling from the Mutriba (Santonian) to Burgan (Albina) formations through highly interbedded, high-compressive-strength carbonates (limestone and dolomite), sandstones, and shales. In recent years, Kuwait Oil Company (KOC) has tested many different bit designs in an attempt to minimize stick/slip vibrations and maximize the rate of penetration (ROP). This paper presents the technology used to nearly eliminate stick/slip vibrations, leading to a field record (and a consistent performance) for this application, as well as the process used to develop the technology.

The interval was drilled using a rotary steerable system (RSS) to maximize wellbore quality and to provide consistent build-up rates (BUR) required. Parameters run in this application are often limited because stick/slip becomes uncontrollable when transitioning through the many formation types. In addition, reactive and stressed caving shales are regularly observed in the Ahmadi and Wara formations drilled during the interval. Special care is needed to mitigate these drilling challenges and to successfully drill the interval with low stick/slip vibrations and high ROP.

Using proprietary state-of-the-art design and analysis technologies, a new polycrystalline diamond compact (PDC) bit was designed for use specifically with RSS tools to minimize the vibrations. The solution required a thorough offset analysis before the interval that was presented using the design process. The design process enabled the presentation of a driller's roadmap to be used in conjunction with the new bit to enable a benchmark ROP to be achieved.

The use of the newly designed PDC bit produced minimal torsional vibrations, enabling a 62% increase in ROP over the field average. This increased ROP resulted in a savings of USD 90,000, reducing the cost per foot by 33%, as compared to the field average. The bit also came out in excellent condition, enabling future use in similar applications for KOC.

The Greater Burgan field is under production for more than 60 years and producing light to medium API oil. The objective of this paper is to explain an innovative method adopted in testing of Lower Burgan formation heavy oil and challenges faced during testing.

Heavy-oil zones are identified based on petrophysical logs interpretation and are located mostly near regional original oil-water-contact (OOWC). A previous study done on mapping of heavy oil zone for Burgan reservoirs and based on the maps, new process helped to identify expected heavy Oil zones in the upcoming and existing wells. To sustain future production target raised a need to explore flow potentials in the heavy oil reservoirs. A new methodology was developed by using a specially designed electrical submersible pump (ESP). Special testing pump (ESP) was designed and configured based on low API, high viscous oil, high angle deviation and reservoir characteristics from nearby wells.

The well was tested using specially designed ESP. The well produced for few days with Oil API 19-20 and flowed with a rate of 650-800 BLPD with 40%-50% water cut. In the future, this zone could be put back on production.

Earlier for heavy oil Burgan reservoirs, the oil viscosity and density were measured from downhole fluid sampling in few of the wells. However, there are uncertainties on how oil properties change with pressure. For the first time in Greater Burgan field, using specially designed ESP was a remarkable success for initial testing of heavy oil reservoir close to regional OWC.

A regional study of the Burgan formation has been carried out over the North Kuwait Fields to understand the variation in depositional environment, oil occurrence and control of trapping mechanism on the quality of oil. The Burgan Formation in North Kuwait comprises fluvial, deltaic and marine sediments deposited during the Lower Albian period in response to global changes in sea level. There is a systematic gradation of depositional environments in Burgan during this period. Oil entrapment in this formation shows regional variation. Both stratigraphic and structural controls on oil accumulation are dominant in the region. The oil quality becomes heavier towards North and has a strong structural control. Significant volume of inplace oil has been estimated during this study which would be pursued for commercial exploitation of this deep heavy oil reservoir.

Burgan clastic sedimentation over Shuaiba carbonates was initiated by a regional fall in sealevel and establishment of a deltaic setting. Reservoir facies include mouth bars and distributary channels along with non-reservoir facies of interdistributary bay and shallow marine environments. After a significant hiatus, the braided channel systems with massive amalgamated sand bodies were established in response to significant fall in seal level. Subsequently a significant marker in form of a marine and shoreface sand with associated marine shale was deposited with a rise in sea level. Estuarine channels and bay shales were deposited above this surface. The upper part of Lower Burgan has transgressive sand bodies. The Middle Burgan is dominated by marine shale and shoreface sand deposits in response to further rise in sea level. The Upper part of Burgan is mainly comprising estuarine channel sands and interdistributary bay deposits. In a regional context, the sedimentation pattern shows increasing marine influence to East-Northeast directions.

The oil quality in Burgan is intricately related to the structure and trapping mechanisms. A post Mishrif time tilt in structure has resulted in a deeper relict oil water contact in Lower Burgan towards West of Sabiriyah. In the area towards North of Raudhatain structure, the fluid contact shows significant tilt towards North with a rising structure. The doubly plunging anticlines of Raudhatain and Sabiriyah structures have lighter oil in Burgan formation in a structural trap. Further north of Raudhatain, the oil is heavy although there is lateral reservoir continuity. Significant faults have been mapped in this area. The structure is shallower towards North with progressively deeper fluid contact in Lower Burgan. Origin of heavy oil appears be due to significant spilling of lighter oil along faults and upstructure migration due to structural tilting and transtensional deformation.

Significant accumulation of heavy oil has been established in Basal Burgan, Lower Burgan and Upper Burgan Formations. Heavy oil inflow in form of testing and sampling is seen in 12 wells. Aggressive plans are in place to map the oil quality and to formulate a long term exploitation strategy.

Kuwait has started developing the heavy oil fields in deep wells as part of a national oil production strategy and KPC strategy 2040, in order to maintain its increasing oil production capacity for the next decade. The recovery of heavy oil needs a particularly high level of expertise, optimum technologies and techniques, which are tailored to the distinctive challenges presented with consideration to detailed economic analysis and evaluation.

There are several wells perforated in the desired reservoirs within the potential study area which is under secondary (Progressing Cavity Pump) and natural production phase. The low productivity from oil producers which are completed in Lower Burgan sand which is characterized by very high viscous crude oil around 15,000 cp, a low gas-oil ratio (10-30) with little or no primary drive mechanisms. The project requires that certain challenges must be overcome the following key challenges are identified as:

In the design of this project, the suggested method to be used is a non-thermal optimization process "chemical treatment ". Chemical treatment will be implemented as a technology for a well that stopped producing in 2013. This method has been applied globally and has been proven it has less impact on the environment as per KOC HSE policy. The selected environmentally friendly method has three important mechanisms, which are:

Wettability alteration agent.

Viscosity reducer agent.

Asphaltene inhibitor agent.

KOC has successfully conducted a pilot on 20th October 2016 and the well was put back on to the production phase at almost 300 bbl/day (net oil). The return of investment (ROI) of this pilot was a key calculation in answering the economic question and validating the project. As well as showing the project value and its impact on the margin. The return of investment (ROI) captured within 4 hours of production and the total profit to date is 438,885.52 USD.

Wellbore instability while drilling mechanically weak, unstable or vugular formations has been a problem for decades. The cost of wellbore instability is a major challenge in achieving safe and economical drilling operations. As drilling operations moved into challenging formations in Kuwait, the operator sought to drill the Burgan shale and Shuaiba limestone formations in one section as opposed to the traditional two sections required to isolate each formation separately. This paper focuses on a class of technology additives used to mitigate the challenges of drilling weak and unstable formations.

One approach for drilling micro-fractured shale and weak sands with vugular limestone is to mitigate the invasion of drilling fluids into the formation. Other approaches include: stabilizing the reactive shale by preventing hydration and swelling, improving the filtercake texture and strength, and sealing natural micro-fractures. Drilling fluid invasion can change the pore pressure, which may trigger wellbore instability problems. Thus, using ultra-low invasion drilling fluids, sealing micro-fractures and maximizing shale inhibition are key components for mitigating wellbore instability. Field data for the wells using the ultra-low invasion additives and shale stabilizers is presented and compared with previous wells drilled across Burgan and Shuaiba formations in Kuwait.

The field data demonstrates the successful application of these additives to meet challenging key performance indicators (KPI) when drilling the Burgan shale and the vugular Shuaiba limestone in the same hole section. Using the ultra-low invasion additives along with shale inhibitors and borehole stabilizers, resulted in successful drilling operations with no differential sticking, torque-and-drag issues, sloughing, or tight hole problems as compared with usual incidences of differential sticking, pack-offs, and tight hole in other wells within the area. Using those additives also eliminated the need for a higher density fluid to control micro-fractured and tectonically stressed shales. The addition of the additive combination did not affect the rheological profile of the drilling fluid. Meeting these goals through the use of chemical additives in the drilling fluid reduced both non-productive time and formation damage in a cost-effective manner.

Data from this paper specifically addresses a chemical solution for drilling the Burgan shale formation together with vugular Shuaiba limestone in a major Middle East producing field. However, the technique of mitigating wellbore instability by using this combination of chemical additives is fundamental to safe and economical drilling operations for any depleted, weak or micro-fractured formations globally.